<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      border: solid;
    }

    .container {
      width: 800px;
      height: 800px;
      display: flex;
    }

    .container .left {
      flex: 0 0 200px;
    }

    .container .center {
      flex: auto;
      display: flex;
    }

    .container .right {
      flex: 0 0 200px;
    }


    .container-szx {
      display: flex;
      flex-flow: column;
      background-color: antiquewhite;
      flex-grow: 1;
    }

    .container-szx .top {
      flex: 0 0 200px;
    }

    .container-szx .middle {
      flex: auto;

    }

    .container-szx .bottom {
      flex: 0 0 200px;
    }
  </style>
</head>

<body>
  <div class="container">
    <div class="left">左</div>
    <div class="center">
      <div class="container-szx">
        <div class="top">上</div>
        <div class="middle">中</div>
        <div class="bottom">下</div>
      </div>
    </div>
    <div class="right">右</div>
  </div>
</body>

</html>